Local plasma processing

ABSTRACT

A method and an apparatus for performing the method. The method includes: (a) providing an apparatus, wherein the apparatus comprises (i) a chamber, (ii) a plasma device being in and coupled to the chamber, (iii) a shower head being in and coupled to the chamber, and (iv) a chuck being in and coupled to the chamber; (b) placing the substrate on the chuck; (c) using the plasma device to receive a plasma device gas and generate a plasma; (d) directing the plasma at a pre-specified area on the substrate; and (e) using the shower head to receive and distribute a shower head gas in the chamber, wherein the plasma device gas and the shower head gas are selected such that the plasma and the shower head gas when mixed with each other result in a chemical reaction that forms a film at the pre-specified area on the substrate.

This application is a continuation application claiming priority to Ser.No. 10/908,709, filed May 24, 2005.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to plasma processing, and morespecifically, to local plasma processing.

2. Related Art

In a typical semiconductor structure fabrication process, the depositionof a film on a wafer can frequently result in the film being thinner onthe edge of the wafer than on other parts of the wafer (i.e.,under-deposition at wafer edge). In addition, a chemical mechanicalpolishing (CMP) process performed on the wafer usually has a higher CMPrate at the edge of the wafer than at other parts of the wafer (i.e.,over-polish at wafer edge). As a result, integrated circuits formed nearthe edge of the wafer may be damaged by this nonuniformity.

Therefore, there is a need for a method (and an apparatus for performingthe method) to compensate for the problems of under-deposition andover-polish at the edge of a wafer.

SUMMARY OF THE INVENTION

The present invention provides a structure processing method, comprisingproviding an apparatus, wherein the apparatus comprises (i) a chamber,(ii) a plasma device being in and coupled to the chamber, (iii) a showerhead being in and coupled to the chamber, and (iv) a chuck being in andcoupled to the chamber; placing a substrate on the chuck; using theplasma device to receive a plasma device gas and generate a plasma;directing the plasma at a pre-specified area on the substrate; and usingthe shower head to receive and distribute a shower head gas in thechamber, wherein the plasma device gas and the shower head gas areselected such that the plasma and the shower head gas when mixed witheach other result in a chemical reaction that forms a film at thepre-specified area on the substrate.

The present invention also provides a structure processing method,comprising providing an apparatus, wherein the apparatus comprises (i) achamber, (ii) a plasma device being in and coupled to the chamber, and(iii) a chuck being in and coupled to the chamber; placing a substrateon the chuck; using the plasma device to receive a plasma device gas andgenerate a plasma; and directing the plasma at a pre-specified area onthe substrate, wherein the plasma device gas is selected such thatparticles of the plasma bombard the pre-specified area on the substrateessentially without chemically reacting with materials of thepre-specified area on the substrate.

The present invention provides a method (and an apparatus for performingthe method) to compensate for the problems of under-deposition andover-polish at the edge of a wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an apparatus, in accordance with embodiments of thepresent invention.

FIG. 2 illustrates a plasma device of the apparatus of FIG. 1, inaccordance with embodiments of the present invention.

FIGS. 3-8 illustrate different uses of the apparatus of FIG. 1, inaccordance with embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an apparatus 100, in accordance with embodiments ofthe present invention. In one embodiment, the apparatus 100 comprises achamber 110, a chuck 120, a plasma device 130, and a shower head 140.

The chuck 120 is adapted for holding a wafer 150 for processing. Theplasma device (also called plasma jet) 130 is adapted for receiving aplasma device gas and then generating a plasma at atmospheric pressure(i.e., around 1 atm) for processing a pre-specified area of the wafer150. The shower head 140 is adapted for receiving and distributing ashower head gas into the chamber 110.

FIG. 2 illustrates one embodiment of the plasma device 130 of FIG. 1, inaccordance with embodiments of the present invention. Illustratively,the plasma device 130 comprises (i) a container 210 that also serves asa ground electrode of the plasma device 130, (ii) a radio frequencyelectrode 220, (iii) a gas inlet 230, and (iv) a nozzle 240. The plasmadevice 130 is adapted for receiving the plasma device gas via the gasinlet 230, creating a plasma inside the container 210, and outputtingthe plasma via the nozzle 240.

With reference to FIGS. 1 and 2, in one embodiment, either or both ofthe plasma device 130 and the chuck 120 are moved with respect to thechamber 110 such that the plasma output by the plasma device 130 via thenozzle 240 is directed at the pre-specified area of the wafer 150. Inaddition, the plasma device gas and the shower head gas are selectedsuch that the plasma output by the plasma device 130 and the shower headgas distributed by the shower head 140 when mixed with each other willresult in chemical reactions forming a film (not shown) on thepre-specified area of the wafer 150. After the film is deposited, ifanother film (not shown) is needed at another pre-specified area of thewafer 150, the plasma output is re-directed at the another pre-specifiedarea of the wafer 150.

In an alternative embodiment, the plasma device gas is selected suchthat the plasma output by the plasma device 130 contains high iondensities that (i) drive off volatile constituents on the wafer 150(i.e., drying) or (ii) modify a thin film (not shown) for the purpose ofdensification, annealing, curing, or cross-linking in the case ofpolymeric systems on the wafer 150. For example, in one embodiment, theplasma device gas includes inert gases (e.g., Ar, etc.) or N₂ so thatthe resultant plasma contains radicals that drive off rinsing speciesfrom the pre-specified area of the wafer 150. After the pre-specifiedarea of the wafer 150 is dried off, if another pre-specified area of thewafer 150 needs drying, either or both of the plasma device 130 and thechuck 120 are moved with respect to the chamber 110 such that the plasmaoutput by the plasma device 130 via the nozzle 240 is directed at theanother pre-specified area of the wafer 150. The same plasma device gas(i.e., Ar or N₂) can be used to densify, anneal, cure, or cross-link afilm on the wafer 150 by heating the film to a high temperature. Itshould be noted that the plasma device gas is also selected such thatthe resultant plasma essentially does not chemically react with anymaterial of the wafer 150.

In one embodiment, the shower head 140 is omitted if the apparatus 100of FIG. 1 is to be used to (i) drive off volatile constituents on thewafer 150 (i.e., drying) or (ii) densify, anneal, cure, or cross-link afilm on the wafer 150 by heating the film to a high temperature.

FIGS. 3-8 illustrate different uses of the apparatus 100 of FIG. 1, inaccordance with embodiments of the present invention. More specifically,with reference to FIG. 3, the apparatus 100 (FIG. 1) is used fordepositing a film 320 at a pre-specified location on the wafer 150. Forsimplicity, hereafter, only the plasma device 130 instead of the entireapparatus 100 of FIG. 1 is shown in the figures. The positions of theplasma device 130 and/or the chuck 120 with respect to the chamber 110are such that the nozzle 240 is pointed to the pre-specified location onthe wafer 150. In one embodiment, when the plasma generated by theplasma device 130 exits the plasma device 130 at the nozzle 240, theplasma is mixed with the shower head gas distributed by the shower head140 resulting in chemical reactions producing a material that depositson the pre-specified location on the wafer 150 as the film 320. Thematerial may also deposit at other areas of the wafer 150 but withnegligible amounts.

FIG. 4 is a table listing some illustrative film materials of the film320 (FIG. 3) and the corresponding plasma device gas and shower head gasthat may be used to create the film 320 (FIG. 3). With reference to bothFIGS. 3 and 4, for instance, assume the film 320 is to comprise silicondioxide (SiO₂). Then, silane (SiH₄) may be used as the showerhead gas,and one or more of the group comprising O₂, N₂O, NO, CO₂, and CO may beused as the plasma device gas. For instance, if oxygen (O₂) is used asthe plasma device gas, then the following chemical reaction occursoutside the nozzle 240 where the oxygen plasma exits the plasma device130 and is mixed with the showerhead gas: SiH₄+O₂→SiO₂+2H₂. As a result,the resultant SiO₂ deposits on the pre-specified location on the wafer150. In one embodiment, the pressure of the ambient inside the chamber110 (FIG. 1) is atmospheric (i.e., 1 atm) during the deposition. Theflow rate for oxygen (plasma device gas) in the plasma device 130 is ina range of 10-1,000 sccm (Standard Cubic Centimeters per Minute). Theflow rate of silane (showerhead gas) is in a range of 10-1,000 sccm. Tomaintain the chamber 110 (FIG. 1) at atmospheric pressure, a dilutantgas (e.g., oxygen in this example) may be added in the showerhead gas(in addition to silane) at a flow rate in a range of 100-10,000 sccm.

As another example, assume the film 320 is to comprise tungsten (W).Then, inert gas (e.g., argon) and hydrogen (H₂) may be used as theshowerhead gas, and WF₆ may be used as the plasma device gas. Then, thefollowing chemical reaction occurs outside the nozzle 240 where theplasma exits the plasma device 130 and is mixed with the showerhead gas:WF₆+3H₂→W+6HF. As a result, the resultant tungsten (W) deposits on thepre-specified location on the wafer 150.

With reference to FIG. 3, in one embodiment, the film 320 is formed atthe edge of the wafer 150 so as to compensate for under-depositionand/or over-polish (i.e., over-planarization) at the edge of the wafer150. In general, films (not shown) similar to the film 320 may be formedat locations (not necessarily at the wafer edge) of the wafer 150 thatare thinner than average so as to compensate for an earlier over-etchingand/or a subsequent under-deposition at these locations (over-etchingand under-deposition may occur due to pattern/topology nonuniformity).For example, assume a tungsten layer (not shown) deposited on the wafer150 using a traditional deposition method is thinner at first areas ofhigh device density than at second areas of low device density. Then,the apparatus 100 of FIG. 1 may be used to deposit more tungsten (W) atthe first areas where the W layer is thinner so as to compensate for theearlier under-deposition of tungsten there.

In one embodiment, the plasma device 130 can be stationary (i.e., fixed)with respect to the chamber 110 (FIG. 1) while the wafer 150 is rotatedaround an axis perpendicular to the wafer 150. Deposition time is suchthat the resultant film 320 has a thickness 322 not less than therequired minimum thickness. For example, assume that a typical SiO₂ film(not shown) deposited on top of the wafer 150 must have a thickness ofat least 20 nm, and that the apparatus 100 (FIG. 1) deposits SiO₂ at 2nm/wafer rotation. As a result, the deposition time (in terms ofrotations) must be at least: 20 nm/(2 nm/rotation)=10 rotations in thisexample. Assume further that it takes 1 sec for the wafer 150 to makeone rotation. Then, the deposition time must be at least: 10 rotations×1sec/rotation=10 sec.

FIG. 5 illustrates another use of the apparatus 100 (FIG. 1), inaccordance with embodiments of the present invention. More specifically,a chip 505 including a copper wire bond landing pad 510 and a gold wirebond 520 is placed on the chuck 120 of the apparatus 100 (FIG. 1). Then,a SiO₂ film 530 is deposited so as to seal off the connection betweenthe copper pad 510 and the gold wire bond 520. As a result, theconnection between the copper pad 510 and the gold wire bond 520 isprotected from corrosion. In an alternative embodiment, the film 530comprises SiN (silicon nitride) instead of SiO₂. In yet anotheralternative embodiment, the film 530 comprises first and second layers(not shown) of SiN and SiO₂, respectively, with the first layer of SiNbeing sandwiched between and in direct physical contact with the copperwire bond landing pad 510 and the second layer of SiO₂. Illustratively,the apparatus 100 (FIG. 1) can be used to form the first layer of SiN onthe copper wire bond landing pad 510 first, and then form the secondlayer of SiO₂ on the first layer of SiN resulting in the film 530.

FIG. 6 illustrates yet another use of the apparatus 100 (FIG. 1), inaccordance with embodiments of the present invention. More specifically,the apparatus 100 of FIG. 1 is used to deposit a SiO₂ film 620 so as topassivate (seal off) a top surface of a crackstop/through via 610 so asto protect the crackstop/through via 610 from corrosion. Thecrackstop/through via 610 usually comprises an electrically conductingmaterial (e.g., Al, Cu, and W). Therefore, the SiO₂ film 620 helpsprevent corrosion of this electrically conducting material. In analternative embodiment, the film 620 comprises SiN (silicon nitride)instead of SiO₂. In yet another alternative embodiment, the film 620comprises third and fourth layers (not shown) of SiN and SiO₂,respectively, with the third layer of SiN being sandwiched between andin direct physical contact with the crackstop/through via 610 and thefourth layer of SiO₂. Illustratively, the apparatus 100 (FIG. 1) can beused to form the third layer of SiN on the crackstop/through via 610first, and then form the fourth layer of SiO₂ on the third layer of SiNresulting in the film 620.

FIG. 7 illustrates yet another use of the apparatus 100 (FIG. 1), inaccordance with embodiments of the present invention. More specifically,the apparatus 100 of FIG. 1 is used to precisely deposit a SiO₂ ring 720on the wafer 150. Then, a chip 730 is placed on the wafer 150 and insidethe ring 730. In other words, the ring 720 serves as a positioningreference for the placing of the chip 730. Because the SiO₂ ring 720 canbe placed on the wafer 150 at a pre-specified location with highprecision, the chip 730 can be placed on the wafer 150 at the specifiedlocation also with high precision.

FIG. 8 illustrates yet another use of the apparatus 100, in accordancewith embodiments of the present invention. More specifically, theapparatus 100 of FIG. 1 is used to deposit a ring 820 at a pre-specifiedlocation on the wafer 150. Then, a cooling pad 830 is placed on the ring820 without being in direct physical contact with the wafer 150. Thecooling pad 830 is adapted for absorbing the heat generated by devices(not shown) formed on the wafer 150 directly beneath the cooling pad830. In one embodiment, the ring 820 comprises SiO₂.

In summary, with reference to FIG. 1, the apparatus 100 may be used todeposit films of different materials at pre-specified locations on thewafer 150. The apparatus 100 may also be used to (i) drive off volatileconstituents on the wafer 150 (i.e., drying) or (ii) modify a thin film(e.g., densification, annealing, curing, or cross-linking of the film)on the wafer 150.

In one embodiment, the apparatus 100 has multiple plasma devices (notshown) similar to the plasma device 130 so that (a) multiple films (notshown) similar to the film 320 (FIG. 3) can be simultaneously formed ondifferent pre-specified locations of the wafer 150, and (b) differentpre-specified locations of the wafer 150 can be simultaneously dried bydirecting the plasma outputs of the multiple plasma devices at thedifferent pre-specified locations of the wafer 150.

While particular embodiments of the present invention have beendescribed herein for purposes of illustration, many modifications andchanges will become apparent to those skilled in the art. Accordingly,the appended claims are intended to encompass all such modifications andchanges as fall within the true spirit and scope of this invention.

1. A structure processing method, comprising: providing an apparatus,wherein the apparatus comprises: (i) a chamber, (ii) a plasma devicebeing in and coupled to the chamber, (iii) a shower head being in andcoupled to the chamber, and (iv) a chuck being in and coupled to thechamber; placing a substrate on the chuck; using the plasma device toreceive a plasma device gas and generate a plasma; directing the plasmaat a pre-specified area on the substrate; and using the shower head toreceive and distribute a shower head gas in the chamber, wherein theplasma device gas and the shower head gas are selected such that theplasma and the shower head gas when mixed with each other result in achemical reaction that forms a film at the pre-specified area on thesubstrate.
 2. The method of claim 1, wherein the film has apre-specified thickness so as to compensate for the non-uniformity of asubsequent planarization process to be performed on the substrate. 3.The method of claim 1, wherein the film has a pre-specified thickness soas to compensate for the non-uniformity of an earlier deposition processperformed on the substrate.
 4. The method of claim 1, wherein the plasmadevice gas comprises silane, wherein the shower head gas comprisesoxygen atoms, and wherein the film comprises silicon dioxide.
 5. Themethod of claim 1, wherein the plasma is generated at an atmosphericpressure.
 6. The method of claim 1, wherein the pre-specified area is atan edge of the substrate.
 7. The method of claim 1, wherein thesubstrate comprises a semiconductor chip including (i) a metallic wirebond pad and (ii) a wire bond coupled to the pad, and wherein the filmpassivates a connection between the copper pad and the wire bond.
 8. Themethod of claim 1, wherein the film passivates a top surface of a crackstop in the substrate.
 9. The method of claim 1, wherein the filmpassivates a top surface of a through via in the substrate.
 10. Themethod of claim 1, wherein the apparatus further comprises anotherplasma device being in and coupled to the chamber, wherein the methodfurther comprises: using the another plasma device to receive the plasmadevice gas and generate another plasma, and directing the another plasmaat another pre-specified area on the substrate so as to form anotherfilm at the another pre-specified area on the substrate.
 11. The methodof claim 1, further comprising re-directing the plasma at anotherpre-specified area on the substrate to form another film at the anotherpre-specified area on the substrate.
 12. A structure processing method,comprising: providing an apparatus, wherein the apparatus comprises: (i)a chamber, (ii) a plasma device being in and coupled to the chamber, and(iii) a chuck being in and coupled to the chamber; placing a substrateon the chuck; using the plasma device to receive a plasma device gas andgenerate a plasma; and directing the plasma at a pre-specified area onthe substrate, wherein the plasma device gas is selected such thatparticles of the plasma bombard the pre-specified area on the substrateessentially without chemically reacting with materials of thepre-specified area on the substrate.
 13. The method of claim 12, whereinthe plasma device gas comprises a gas selected from the group consistingof Ar and N₂.
 14. The method of claim 12, wherein the plasma isgenerated at an atmospheric pressure.
 15. The method of claim 12,further comprising re-directing the plasma at another pre-specified areaon the substrate.
 16. The method of claim 15, wherein said re-directingthe plasma comprises: keeping the plasma device stationary with respectto the chamber; and moving the substrate with respect to the chamber.